BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a curable resin composition, a water-soluble ink
composition, an ink set, and an image-forming method.
2. Description of the Related Art
[0002] A curable resin composition, which crosslinks a binder and the like in association
with a polymerizable compound having an ethylenic unsaturated group as a crosslinking
agent when imparted with energy such as light or heat and is cured, has been widely
used for industrial usages such as a coating material, paint, printing ink, an adhesive,
an optical material, a laminating material for electronic products, an electrical
insulating material, and a resist material. A cross-linking compound is cured when
irradiated with an active energy ray such as an ultraviolet ray. For example, the
cross-linking compound as a curing agent or a crosslinking agent is blended into ink
or paint, and after an image is formed, the cross-linking compound is polymerized
by being irradiated with an ultraviolet ray or the like so as to form a cured film,
thereby improving the weather resistance or durability of the image.
[0003] Among the curable resin compositions, for ink compositions, recently, there has been
a demand for reducing a volatile organic compound (VOC), which has been widely used
in the related art as a solvent or the like, from the viewpoint of environmental protection
or safety, and accordingly, a waterborne photocurable system capable of reducing the
usage amount of the VOC is attracting attention. Even in the field of printing ink,
there have been a variety of proposals regarding waterborne photocurable ink in which
a water-soluble solvent such as water or an alcohol is used as a medium, and the curable
resin compositions are also applied to ink jet recording methods.
[0004] In the ink jet recording method, since a printing apparatus is inexpensive, no plate
is required during printing, and an image is directly formed on a recording medium
by discharging ink only to required image sections, ink can be efficiently used, and
there is an advantage of having inexpensive operational costs particularly in the
case of small lot production. Furthermore, only a small amount of noise is generated,
and recently, the method has been attracting attention as an excellent image-recording
method.
[0005] In ink for photocurable ink jet recording, generally, an image is formed using an
aqueous ink containing a polymerizable compound and a polymerization initiator, and
the image is cured and fixed by radiating light. Light in the ultraviolet (UV) range
is generally used as a light source. Since a majority of ink components is cured through
light radiation, drying properties are superior to those of solvent-based ink, images
do not easily bleed, and thus the ink can be printed on a variety of recording media,
which makes the ink jet recording method excellent.
[0006] In the above-described waterborne ink for photocurable ink jet recording, a water-soluble
photopolymerization initiator is used; however, among photopolymerization initiators
that are commercially available at the present time, only a limited range of photopolymerization
initiators such as α-hydroxyacetophenone-based initiators are being used, and the
degree of solubility in water is also insufficient. As a result, there has been a
proposal regarding the introduction of an ionic substituent such as carboxylate or
sulfonate (refer to
JP1994-228218A (
JP-H6-228218A),
JP2008-247939A, and
BR2108487B), but the temporal stability of ink easily degrades (ink easily aggregates), and
it cannot be said that this method has been satisfactory at all times. In addition,
recently, there has been a proposal (refer to
JP2012-7071A) regarding an ink composition in which a thioxanthone photopolymerization initiator
containing a salt of a hydroxyl group, a carboxyl group, or a sulfo group and an α-aminoacetophenone
photopolymerization initiator containing a salt of a hydroxyl group, a carboxyl group,
or a sulfo group are jointly used, but there has been a demand for performance to
be further improved.
SUMMARY OF THE INVENTION
[0007] An object of the present invention is to provide a curable resin composition, a water-soluble
ink composition, an ink set, and an image-forming method in which both a high sensitivity
with respect to ultraviolet rays and a high degree of solubility in water are provided,
and an adverse influence on the stability of curable resin compositions, particularly,
ink compositions is small.
[0008] The present inventors carried out intensive studies in consideration of the above-described
object. As a result, it was found that a photopolymerization initiator having a betaine
structure has an excellent degree of solubility in water, excellent safety in water-soluble
resin compositions, and furthermore excellent radical initiation performance as a
photopolymerization initiator. The present invention has been completed on the basis
of the above-described finding.
[0009] That is, the above-described object has been achieved by the following means.
- (1) A curable resin composition including fine particles, a polymerizable compound
having an ethylenic unsaturated group, a photopolymerization initiator having a betaine
structure, and water.
- (2) The curable resin composition according to (1) in which the photopolymerization
initiator having a betaine structure has any of a benzophenone skeleton, a thioxanthone
skeleton, a thiochromanone skeleton, a biimidazole skeleton, an α-aminoacetophenone
skeleton, an α-hydroxyacetophenone skeleton, or a benzyl ketal skeleton.
- (3) The curable resin composition according to (1) or (2) in which the betaine structure
of the photopolymerization initiator is represented by at least one of Formulae (1)
to (3) described below.
(In Formulae (1) to (3), each of R1 and R2 independently represents an alkyl group. L1 represents a single bond or a divalent linking group, and L2 represents a divalent linking group.)
- (4) The curable resin composition according to any one of (1) to (3) in which the
fine particles are pigments or resin particles.
- (5) A water-soluble ink composition comprising the curable resin composition according
to any one of (1) to (4).
- (6) The water-soluble ink composition according to (5) in which the fine particles
are pigments.
- (7) The water-soluble ink composition according to (5) or (6) in which at least one
of the polymerizable compounds having an ethylenic unsaturated group is a bi- or more
functional (meth)acrylamide compound.
- (8) An ink set including the water-soluble ink composition according to any one of
(5) to (7) and an acidic ink composition containing an acidic compound having a molecular
weght in a range of 50 to 200 and pKa in water in a range of 1 to 5.
- (9) An image-forming method including an acid treatment step of supplying an acidic
ink composition onto a recording medium; and an ink supply step of supplying the water-soluble
ink composition according to any one of (5) to (7) onto the acid-treated recording
medium to form an image.
- (10) The image-forming method according to (9) in which, in the ink supply step, the
ink is supplied by an ink jet method.
[0010] In the present invention, "(meth)acrylamide" represents either or both of acrylamide
and methacrylamide.
[0011] According to the present invention, it is possible to provide a curable resin composition,
a water-soluble ink composition, an ink set, and an image-forming method in which
both a high sensitivity with respect to ultraviolet rays and a high degree of solubility
in water are provided, and an adverse influence on the stability of curable resin
compositions, particularly, ink compositions is small.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] A curable resin composition of the present invention includes fine particles, a polymerizable
compound having an ethylenic unsaturated group, a photopolymerization initiator having
a betaine structure, and water.
[0013] Hereinafter, the curable resin composition of the present invention will be described.
«Curable resin composition»
<Fine particles>
[0014] The fine particles in the present invention refer to nano-sized organic particles
or inorganic particles, and examples thereof include pigment or resin particles. The
volume average particle diameter of the pigment is preferably in a range of 10 nm
to 200 nm, more preferably in a range of 10 nm to 150 nm, and still more preferably
in a range of 10 nm to 100 nm. The volume average particle diameter of the resin particles
is preferably in a range of 1 nm to 2000 nm, more preferably in a range of 1 nm to
500 nm, and still more preferably in a range of 1 nm to 100 nm.
[0015] There is no particular limitation regarding the particle size distribution, and the
particle size distribution may be wide or monodisperse. In addition, a mixture of
two or more kinds of particles having a monodisperse particle size distribution may
be used.
[0016] The volume average particle diameter and particle size distribution of the fine particles
can be measured using, for example, a light scattering method.
- Pigment -
[0017] The curable resin composition of the present invention includes the fine particles,
and in a case in which the curable resin composition of the present invention is a
water-soluble ink composition, the fine particles are preferably a pigment. In this
case, one or more kinds of pigments may be used. In addition, both a pigment and resin
particles may be included.
[0018] There is no particular limitation regarding the kinds of the pigment, and a well-known
organic or inorganic pigment of the related art can be used. Examples of the pigment
include polycyclic pigments such as azo lake, azo pigments, phthalocyanine pigments,
peryline or perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine
pigments, diketo pyrrolo pyrrole pigments, thioindigo pigments, isoindolinone pigments,
and quinophthalone pigments, dye lakes such as basic dye-type lakes and acidic dye-type
lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and
daylight fluorescent pigments, and inorganic pigments such as titanium oxide, iron
oxide, and carbon black. In addition, any pigments, even pigments that are not described
in the color index, can be used as long as the pigments can be dispersed in a water
phase. Furthermore, the pigments the surface of which is treated using a surfactant,
a macromolecular dispersing agent, or the like, graft carbon, and the like also can
be used.
[0019] Among the above-described pigments, azo pigments, phthalocyanine pigments, anthraquinone
pigments, quinacridone pigments, and carbon black-based pigments are particularly
preferred.
- Resin particles -
[0020] The resin particles used in the present invention refer to particles which are different
from a polymer dispersing agent (a polymer dispersing agent that covers at least a
part of the pigment) and a pigment, and which are not used for coloring or as a color
material.
[0021] For example, in a case in which an image is formed using the ink jet method or the
like, when the ink composition includes the resin particles, the resin particles aggregate
due to an organic acidic compound in a treatment fluid. Therefore, the fixing property
or aggregation rate of the image improves. As described above, in a case in which
the ink composition includes the resin particles, when a recording medium is treated
using a treatment fluid, the aggregation rate is suppressed to a certain extent, and
the spreading of ink droplets is accelerated. This suppresses the surface roughness
of an image or the degradation of the uniformity of an image, which is caused by the
insufficient spreading of ink droplets.
[0022] The resin particles being used are preferably resin particles that are insoluble
or not easily dissolved in water.
[0023] The "being insoluble or not easily dissolved in water" refers to the fact that, when
a resin is dried at 105°C for two hours, and then is dissolved in 100 g of water at
25°C, the amount of the resin dissolved is 15 g or less. From the viewpoint of improving
the continuous discharge property and discharge stability of ink, the amount of the
resin particles dissolved is preferably 10 g or less, more preferably 5 g or less,
and still more preferably 1 g or less. The amount of the resin particles dissolved
refers to the amount of the resin particles dissolved when the resin particles are
100% neutralized using sodium hydroxide or acetic acid depending on the kind of an
acid-generating group in a water-insoluble polymer.
[0024] Examples of the resin particles include particles of thermosetting, thermoplastic,
or denatured resins having an anionic group such as (meth)acryl-based resins, epoxy-based
resins, polyurethane-based resins, polyether-based resins, polyamide-based resins,
unsaturated polyester-based resins, phenol-based resins, silicone-based resins, fluorine-based
resins, polyvinyl-based resins such as vinyl chloride, vinyl acetate, polyvinyl alcohol,
and polyvinyl butyral, polyester-based resins such as alkyd resins and phthalic acid
resins, amino-based resins such as melamine resins, melamine formaldehyde resins,
aminoalkyd-cocondensed resins, and urea resins, and copolymers or mixtures thereof.
Among them, the anionic (meth)acryl-based resins are obtained by, for example, polymerizing
a (meth)acryl monomer having an anionic group [anionic group-containing (meth)acryl
monomer] and, as necessary, another monomer that can copolymerize with the anionic
group-containing (meth)acryl monomer. Examples of the anionic group-containing (meth)acryl
monomer include (meth)acyl monomers having one or more selected from a group consisting
of a carboxyl group, a sulfur group, a phospho group, and salts thereof, and among
them, (meth)acryl monomers having a carboxyl group or a salt thereof (for example,
acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propyl acrylic acid,
isopropyl acrylic acid, itaconic acid, fumaric acid, salts thereof, and the like)
are preferred, and acrylic acid, methacrylic acid, and salts thereof are particularly
preferred.
[0025] In the present invention, from the viewpoint of image-fixing properties and the suppression
of ink jet nozzle clogging, the content of the resin particles in the curable resin
composition, particularly, the ink composition is preferably in a range of 0.01 mass%
to 20 mass%, more preferably in a range of 0.05 mass% to 10 mass%, and particularly
preferably in a range of 0.1 mass% to 5 mass% with respect to the total amount of
the curable resin composition or the ink composition.
[0026] A single kind of the resin particles may be used, or a combination of two or more
kinds may be used.
- Dispersing agent -
[0027] In the curable resin composition of the present invention, particularly, the ink
composition, the pigment is preferably dispersed using a dispersing agent. When the
resin particles can be dispersed on their own, it is not necessary to use a dispersing
agent; however, when the resin particles cannot be dispersed on their own, the resin
particles are preferably dispersed using a dispersing agent.
[0028] Any dispersing agent may be used as long as the dispersing agent is capable of dispersing
the pigment or the resin particles (particularly, the pigment).
[0029] In addition, the dispersing agent may be any of cationic, anionic, and nonionic dispersing
agents.
[0030] Examples of the dispersing agent include dispersing agents for low-molecular surfactants
and polymers, and, in the present invention, polymer dispersing agents are preferred.
Hereinafter, a pigment at least a part of which is coated with the polymer dispersing
agent will also be referred to a "resin-coated pigment".
[0031] Examples of the low-molecular surfactants include the surfactants described in paragraphs
0016 to 0020 of
JP2010-188661A.
[0032] The polymer dispersing agent may be a water-soluble polymer dispersant or a water-insoluble
polymer dispersant.
[0033] A hydrophilic macromolecular compound can be used as the water-soluble polymer dispersing
agent, and examples thereof include the natural hydrophilic macromolecular compounds
described in paragraphs 0021 and 0022 in
JP2010-188661A.
[0034] In addition to the natural hydrophilic macromolecular compound, it is also possible
to use a synthetic hydrophilic macromolecular compound.
[0035] Examples of the synthetic hydrophilic macromolecular compound include macromolecular
compounds having a salt of a cationic functional group in a side chain such as vinyl-based
macromolecules such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl
ether, acryl-based resins such as polyacrylamide, polyacrylic acid or alkali metal
salts thereof, and water-soluble styrene acryl resins, alkali metal salts of water-soluble
styrene maleic acid resins, water-soluble vinyl naphthalene acryl resins, water-soluble
vinyl naphthalene maleic acid resins, polyvinyl pyrrolidone, polyvinyl alcohol, and
β-naphthalene sulfonic acid formalin condensates, quaternary ammonium, and amino groups.
[0036] Among them, from the viewpoint of the dispersion stability and aggregating property
of the pigment, macromolecular compounds having a carboxyl group and a salt thereof
are preferred, and, for example, macromolecular compounds having a carboxyl group
or a salt thereof such as acryl-based resins such as water-soluble styrene acryl resins,
water-soluble styrene maleic acid resins, water-soluble vinyl naphthalene acryl resins,
and water-soluble vinyl naphthalene maleic acid resins are particularly preferred.
[0037] As the water-insoluble dispersing agent among the monomer dispersing agents, it is
possible to use a polymer having both a hydrophobic part and a hydrophilic part. Examples
thereof include styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylic
acid ester copolymers, (meth)acrylic acid ester-(meth)acrylic acid copolymers, polyethylene
glycol (meth)acrylate-(meth)acrylic acid copolymers, styrene-maleic acid copolymers,
and the like.
[0038] Among them, styrene-(meth)acrylic acid copolymers, (meth)acrylic acid ester-(meth)acrylic
acid copolymers, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymers,
and styrene-maleic acid copolymers may be binary copolymers or ternary or more copolymers.
[0039] Among them, as the polymer dispersing agent, (meth)acrylic acid ester-(meth)acrylic
acid copolymers are preferred, and a ternary copolymer of benzyl (meth)acrylate-(meth)acrylate-methyl
(meth)acrylate is particularly preferred.
[0040] Here, (meth)acrylic acid refers to acrylic acid or methacrylic acid, and (meth)acrylate
refers to acrylate or methacrylate.
[0041] The mass average molecular weight of the polymer dispersing agent is preferably in
a range of 3,000 to 200,000, more preferably in a range of 5,000 to 100,000, still
more preferably in a range of 5,000 to 80,000, and particularly preferably in a range
of 10,000 to 60,000.
[0042] The acid value of the polymer dispersing agent is not particularly limited; however,
from the viewpoint of aggregating properties, the acid value thereof is preferably
greater than the acid value of the resin particles described below (preferably self-dispersing
resin particles).
[0043] In the curable resin composition of the present invention, particularly, the ink
composition, the mass ratio of the pigment to the dispersing agent (pigment:dispersing
agent) is preferably in a range of 1:0.06 to 1:3, more preferably in a range of 1:0.125
to 1:2, and still more preferably in a range of 1:0.125 to 1:1.5.
[0044] The average particle diameter of the pigment (the average particle diameter of the
resin-coated pigment in the case of the resin-coated pigment) is preferably in a range
of 10 nm to 200 nm, more preferably in a range of 10 nm to 150 nm, and still more
preferably in a range of 10 nm to 100 nm. When the average particle diameter is 200
nm or less, the color reproducibility becomes favorable, the ink strike characteristics
becomes favorable when ink droplets are stricken using the ink jet method, and, when
the average particle diameter is 10 nm or more, the light resistance becomes favorable.
The particle size distribution of the pigment is not particularly limited, and may
be any of a wide particle size distribution or a monodisperse particle size distribution.
In addition, a mixture of two kinds of pigments having a monodisperse particle size
distribution may be used.
[0045] The average particle diameter and particle size distribution of the pigment can be
obtained by measuring the volume average particle diameter through a dynamic light
scattering method using a nanotrack particle size distribution measuring apparatus
UPA-EX150 (manufactured by Nikkiso Co., Ltd.).
[0046] In the present invention, from the viewpoint of the image density, the content of
the pigment in the curable resin composition, particularly, the ink composition is
preferably in a range of 1 mass% to 25 mass%, more preferably in a range of 2 mass%
to 20 mass%, and particularly preferably in a range of 2 mass% to 10 mass% with respect
to the total amount of the curable resin composition or the ink composition.
[0047] A single kind of the pigment may be used, or a combination of two or more kinds may
be used.
[0048] In the curable resin composition of the present invention, particularly, the ink
composition, the mass ratio of the resin particles to the dispersing agent (resin
particles:dispersing agent) is preferably in a range of 1:0 to 1:3, more preferably
in a range of 1:0 to 1:2, and still more preferably in a range of 1:0 to 1:1.5.
<Polymerizing compound having an ethylenic unsaturated group>
[0049] The polymerizable compound having an ethylenic unsaturated group is a compound having
at least one ethylenic unsaturated bond that can radical-polymerize in a molecule,
and there is no particular limitation as long as the polymerization reaction of the
compound can be initiated using a photopolymerization initiator. In addition, the
polymerizable compound may be any of a monomer, an oligomer, a polymer, and the like.
[0050] The ethylenic unsaturated group refers to a group having a carbon-carbon double bond,
and the carbon-carbon double bond may be conjugated with other saturated bonds, but
does not have any double bond in a stable aromatic ring such as a benzene ring.
[0051] Examples of the ethylenic unsaturated group include groups having a partial structure
of -C(=O)CH=CHC(=O)- such as a vinyl group (-CH=CH
2), a (meth)acryloyl group [-C(=O)CH=CH
2, -C(=O)C(CH
3)=CH
2], a vinyl sulfonyl group (-SO
2CH=CH
2), or maleimide.
[0052] Here, examples of the vinyl group include -O-CH=CH
2, >N-CH=CH
2, -S-CH=CH
2, -O-CH
2CH=CH
2, -CH=CH
2 in styrene, and the like, and examples of the (meth)acryloyl group include a (meth)acryloyl
group, a (meth)acryloyloxy group, a (meth)acryloylamide group, and the like.
[0053] The polymerizable compound having the ethylenic unsaturated group is preferably a
compound having a carbon-carbon double bond at the terminal in the molecule or a compound
having a maleimide cyclic group in the molecule.
[0054] The polymerizable compound having the ethylenic unsaturated group is preferably a
water-soluble compound from the viewpoint of the discharge stability of the curable
resin composition, particularly, the ink composition. The degree of solubility of
the polymerizable compound having the ethylenic unsaturated group is not particularly
limited, but the degree of solubility in water at 25°C is preferably 2 mass% or more,
more preferably 5 mass% or more, still more preferably 10 mass% or more, and particularly
preferably 20 mass% or more, and a homogeneous mixture of the polymerizable compound
having the ethylenic unsaturated group with water at an arbitrary ratio is most preferred.
[0055] Specific examples of the polymerizable compound include (meth)acrylamide compounds,
(meth)acrylate compounds, vinyl compounds, maleimide compounds, vinyl sulfone compounds,
N-vinylamide compounds, and the like. The compound is preferably a di- or more functional
compound, more preferably a (meth)acrylamide compound, a (meth)acrylate compound,
or a vinyl compound, and particularly preferably a bi- or more functional (meth)acrylamide
compound. In addition, in the ink composition of the present invention, the polymerizable
compound may be singly used, or two or more kinds of the polymerizable compounds may
be jointly used. In a case in which two or more kinds of the polymerizable compounds
are jointly used, it is preferable to use a mixture of two or more kinds selected
from (meth)acrylamide compounds, (meth)acrylate compounds, vinyl compounds, maleimide
compounds, vinyl sulfone compounds, and N-vinylamide compounds, and, among them, it
is more preferable to use a mixture in which at least one kind of the polymerizable
compound is a (meth)acrylamide compound.
[0056] From the viewpoint of improving the water solubility, the polymerizable compound
may have a poly(ethyleneoxy) chain, a poly(propyleneoxy) chain, an ionic group (for
example, a carboxyl group, a sulfo group, or the like), a hydroxyl group, or the like.
[0058] From the viewpoint of curing properties and solubility, monomers 21, 27, 28, 42,
44, and 51 are preferred.
[0060] As the (meth)acrylamide compound, it is possible to use any of a monofunctional (meth)acrylamide
compound [compound having a (meth)acrylate group] and a polyfunctional (meth)acrylamide
compound, and a polyfunctional (meth)acrylamide compound is preferred.
[0061] Specific examples of the monofunctional (meth)acrylate compound include isoamyl (meth)acrylate,
stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate,
decyl (meth)acrylate, isoamylstyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyldiglycol
(meth)acrylate, 2-hydroxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxydiethyleneglycol
(meth)acrylate, methoxypolyethyleneglycol (meth)acrylate, methoxypropyleneglycol (meth)acrylate,
tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate,
2-hydroxypropyl (meth)acrylate, 2-(meth)acryloxyethylsuccinic acid, 2-(meth)acryloxyethyl-2-hydroxyethyl-phthalic
acid, lactone denatured flexible (meth)acrylate, t-butylcyclohexyl (meth)acrylate,
2-(2-ethoxyethoxy)ethyl acrylate, cyclopentenyl acrylate, cyclopentenyloxyethyl acrylate,
dicyclopentanyl acrylate, and the like.
[0062] Specific examples of the polyfunctional (meth)acrylate compound include bis(4-acryloxypolyethoxyphenyl)propane,
neopentyl glycol di(meth)acrylate, ethoxylated (2) neopentyl glycol di(meth)acrylate
(a compound obtained by diacrylating neopentyl glycol ethylene oxide 2 mol adduct),
propoxylated (2) neopentyl glycol di(meth)acrylate (a compound obtained by diacrylating
neopentyl glycol propylene oxide 2 mol adduct), 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol
di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate,
triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene
glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol
di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate,
pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol
tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate,
tetramethylolmethane tri(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate,
denatured glycerine tri(meth)acrylate, denatured bisphenol A di(meth)acrylate, propylene
oxide (PO) adduct di(meth)acrylate of bisphenol A, ethylene oxide (EO) adduct di(meth)acrylate
of bisphenol A, dipentaerythritol hexa(meth)acrylate, caprolactone-denatured dipentaerythritol
hexa(meth)acrylate, and the like.
[0063] The content of the polymerizable compound having the ethylenic unsaturated group
in the curable resin composition, particularly, the ink composition is preferably
in a range of 1 mass% to 50 mass%, more preferably in a range of 1 mass% to 40 mass%,
and still more preferably in a range of 1 mass% to 30 mass% with respect to the total
amount of the solid content of the composition.
[0064] In the present specification, "the total amount of a solid content" or "the total
solid content" refers to the total mass of all components in a composition excluding
a solvent component.
<Photopolymerization initiator>
[0065] At least one kind of the polymerization initiator used in the present invention has
a betaine structure.
[0066] In addition, in the present invention, when the polymerization initiator has a betaine
structure, the skeleton of the photopolymerization initiator may be any photo radical
polymerization initiator skeleton.
[0067] Examples thereof include (a) aromatic ketones, (b) acylphosphine compounds, (c) aromatic
onium salt compounds, (d) organic peroxide, (e) thio compounds, (f) hexaarylbiimidazole
compounds, (g) ketoxime ester compounds, (h) borate compounds, (i) azinium compounds,
(j) metallocene compounds, (k) active ester compounds, (1) compounds having a carbon
halogen bond, (m) alkylamine compounds, and the like. More specific examples thereof
include the polymerization initiators and the like described in "
Ultraviolet curing system" by Kato Kiyomi, pp. 65 to 148, and published by United
Engineering Center (1989), and the like.
[0068] Among them, from the viewpoint of being highly stable in water (not easily being
hydrolyzed), a benzophenone skeleton, a thioxanthone skeleton, a thiochromanone skeleton,
a biimidazole skeleton, an α-aminoacetophenone skeleton, an α-hydroxyacetaphenone
skeleton, or a benzyl ketal skeleton is preferred, and compounds represented by Formulae
(A) to (G) are preferred.
[0069] In Formulae (A) to (G), each of R
a1, R
a2, R
b1 to R
b6, R
c1, R
c2, R
e1, and R
e2 independently represents a substituent. Each of R
d1 and R
d2 independently represents a hydrogen atom or a substituent. Here, R
d1 and R
d2 may be bonded to each other so as to form a ring. Each of n1 and n2 independently
represents an integer of 0 to 5, and each of n3 and n4 independently represents an
integer of 0 to 4. n1+n2 is in a range of 1 to 10, and n3+n4 and n3+n5 are in a range
of 1 to 8.
[0070] Any one of R
a1 and R
a2 in Formulae (A), (B), and (C), R
b1 to R
b6 in Formulae (D), R
a1, R
c1, R
c2, R
d1, and R
d2 in Formulae (E), R
a1, R
c1, and R
c2 in Formulae (F), R
a1, R
a2, R
e1, and R
e2 in Formulae (G) is a substituent having a betaine structure.
[0071] Each of R
a1 and R
a2 is preferably an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an
alkylthio group, an alkyl amino group, an aryl amino group, an ammonio group, or a
halogen atom, all of which have 1 to 10 carbon atoms.
[0072] Each of R
b1 to R
b6 is preferably an alkyl group or an aryl group which have 1 to 10 carbon atoms, and
more preferably an aryl group.
[0073] Each of R
c1, R
c2, R
e1, and R
e2 is preferably an alkyl group having 1 to 4 carbon atoms.
[0074] Each of R
d1 and R
d2 is preferably an alkyl group having 1 to 8 carbon atoms.
- Betaine structure -
[0075] The betaine structure is a structure having a cationic portion and an anionic portion,
the betaine structure may be present in one substituent, or an anionic group and a
cationic group may be separately present at different groups.
[0076] The cationic portion is preferably an onium such as ammonium or sulfonium, and ammonium
is preferred. Examples of the anionic portion include a sulfo group or anions thereof,
a carboxyl group or anions thereof, and a phosphor group or anions thereof.
[0077] In the present invention, the anionic portion and the cationic portion are preferably
present in the same group.
[0078] Examples of structures having the anionic portion and the cationic portion in the
same group include structures having the cationic group at the terminal of the group
and structures having the anionic group at the terminal of the group, and, in the
present invention, structures having the anionic group at the terminal are preferred.
[0079] The structures having the anionic portion and the cationic portion in the same group
are preferably structures represented by Formulae (1) to (3) described below.
[0080] In Formulae (1) to (3), each of R
1 and R
2 independently represents an alkyl group. L
1 represents a single bond or a divalent linking group, and L
2 represents a divalent linking group.
[0081] In R
1 and R
2, the number of carbon atoms in the alkyl group is preferably in a range of 1 to 6,
more preferably in a range of 1 to 4, and particularly preferably 1 or 2.
[0082] Each of L
1 and L
2 is preferably an alkylene group, an arylene group, -O-, -S-, -N(Ra)-, or a divalent
group obtained by combining them. Here, Ra represents a hydrogen atom, an alkyl group,
or an aryl group.
[0083] The number of carbon atoms in the alkylene group is preferably in a range of 1 to
8, more preferably in a range of 1 to 6, and still more preferably in a range of 1
to 4.
[0084] L
1 is preferably a single bond, -O-alkylene-, -S-alkylene-, or -N(Ra)-alkylene-, and
L
2 is preferably an alkylene group.
[0086] The photopolymerization initiators can be easily synthesized by acting a sultone,
a lactone, or the like on a corresponding dimethylamine derivative (obtained by a
well-known reaction such as a reaction between an alcohol body, a phenol body, or
a thiophenone body and N,N-dimethylamino ethyl chloride or a reaction between a bromobenzyl
body and dimethylamine).
[0087] The photopolymerization initiator contains at least one photopolymerization initiator
having the betaine structure, and two or more kinds of photopolymerization initiators
having the betaine structure may be jointly used, or a photopolymerization initiator
having the betaine structure and a photopolymerization initiator not having the betaine
structure may be jointly used. In this case, the photopolymerization initiator not
having the betaine structure is preferably a compound represented by Formula (A) to
(G) in which R
a1, R
a2, R
b1 to R
b6, R
c1, R
c2, R
e1, R
e2, R
d1, and R
d2 are not groups having the betaine structure.
[0088] The total content of the photopolymerization initiator is preferably in a range of
0.1 mass% to 40 mass%, more preferably in a range of 1 mass% to 30 mass%, and still
more preferably in a range of 5 mass% to 20 mass% with respect to the total amount
of the solid content in the curable resin composition, particularly, the ink composition.
[0089] In addition, the content of the photopolymerization initiator is preferably in a
range of 0.1 parts by mass to 30 parts by mass, more preferably in a range of 1 part
by mass to 20 parts by mass, and still more preferably in a range of 5 parts by mass
to 15 parts by mass with respect to 100 parts by mass of the polymerizable compound
having the ethylenic unsaturated group.
[0090] In the present invention, from the viewpoint of the suppression of volatilization
and the improvement in the degree of solubility and sensitivity, the molecular weight
of the photopolymerization initiator represented by Formula (A) is preferably in a
range of 200 to 1500, more preferably in a range of 200 to 1000, and still more preferably
in a range of 200 to 500.
[0091] In the present invention, from the viewpoint of the suppression of volatilization
and the improvement in the degree of solubility and sensitivity, the molecular weight
of the photopolymerization initiator represented by Formula (B) is preferably in a
range of 200 to 1500, more preferably in a range of 200 to 1000, and still more preferably
in a range of 200 to 600.
[0092] In the present invention, from the viewpoint of the suppression of volatilization
and the improvement in the degree of solubility and sensitivity, the molecular weight
of the photopolymerization initiator represented by Formula (C) is preferably in a
range of 150 to 1500, more preferably in a range of 150 to 1000, and still more preferably
in a range of 200 to 600.
[0093] In the present invention, from the viewpoint of the suppression of volatilization
and the improvement in the degree of solubility and sensitivity, the molecular weight
of the photopolymerization initiator represented by Formula (D) is preferably in a
range of 600 to 2000, more preferably in a range of 600 to 1500, and still more preferably
in a range of 600 to 1200.
[0094] In the present invention, from the viewpoint of the suppression of volatilization
and the improvement in the degree of solubility and sensitivity, the molecular weight
of the photopolymerization initiator represented by Formula (E) is preferably in a
range of 250 to 1500, more preferably in a range of 250 to 1000, and still more preferably
in a range of 250 to 600.
[0095] In the present invention, from the viewpoint of the suppression of volatilization
and the improvement in the degree of solubility and sensitivity, the molecular weight
of the photopolymerization initiator represented by Formula (F) is preferably in a
range of 200 to 1500, more preferably in a range of 200 to 1000, and still more preferably
in a range of 200 to 500.
[0096] In the present invention, from the viewpoint of the suppression of volatilization
and the improvement in the degree of solubility and sensitivity, the molecular weight
of the photopolymerization initiator represented by Formula (G) is preferably in a
range of 250 to 1500, more preferably in a range of 250 to 1000, and still more preferably
in a range of 250 to 800.
<Surfactant>
(Surfactant)
[0097] The ink composition or the treatment fluid in the present invention may include at
least one surfactant. The surfactant can be used as a surface tension adjuster. Examples
of the surface tension adjuster include nonionic surfactants, cationic surfactants,
anionic surfactants, betaine surfactants, and the like. From the viewpoint of ink
stability, nonionic surfactants and betaine surfactants are preferred.
[0098] As the specific examples of the surfactants, in hydrocarbon systems, an anionic surfactant
such as a fatty acid salt, an alkyl sulfate ester salt, alkyl benzene sulfonate, an
alkyl naphthalene sulfonic acid salt, a dialkyl sulfosuccinate salt, an alkyl phosphoric
acid ester salt, a naphthalene sulfonic acid formalin condensate, or a polyoxyethylene
alkyl sulfuric acid ester salt, or a nonionic surfactant such as polyoxyethylene alkyl
ether, polyoxyethylene alkyl allyl ether, polyoxyethylene fatty acid ester, sorbitan
fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxy ethylene alkylamine,
glycerin fatty acid ester, or an oxyethylene oxypropylene block copolymer is preferred.
In addition, SURFYNOLS (produced by Air Products and Chemicals, Inc.), which is an
acetyl-based polyoxyethylene oxide surfactant, is also preferably used. In addition,
an amineoxide-type ampholytic surfactant such as N,N-dimethyl-N-alkylamineoxide or
an alkyl sulfobetaine-type ampholytic surfactant such as dimethylbenzyl ammonium propane
sulfonate is also preferred.
[0100] In addition, examples of the surfactant also include the fluorine (alkyl fluoride)-based
surfactants, silicone-based surfactants, and the like described in
JP2003-322926A,
JP2004-325707A, and
JP2004-309806A.
[0101] The content of the surfactant in the ink composition or the treatment fluid is not
particularly limited, but a content at which the surface tension reaches 40 mN/m or
more is preferred, a content at which the surface tension reaches 40 mN/m to 60 mN/m
is more preferred, and a content at which the surface tension reaches 42 mN/m to 50
mN/m is still more preferred.
<Water>
[0102] The curable resin composition of the present invention includes water. The water
being used is preferably water containing no ionic impurities such as ion exchange
water or distilled water.
[0103] The content of water can be appropriately selected depending on the purpose, and
is preferably in a range of 10 mass% to 95 mass%, and more preferably in a range of
30 mass% to 90 mass% with respect to the total mass of the curable resin composition,
particularly, the ink composition.
<Others>
[0104] In addition to the above-described components, the curable resin composition of the
present invention may include, as necessary, an organic solvent, for example, a water-soluble
solvent (an alcohol compound such as methanol or ethanol, a ketone compound such as
acetone or methyl ethyl ketone, an amid compound such as dimethyl formaldehyde, a
nitrile compound such as acetonitrile, a sulfo compound such as sulfolane, or the
like), an antioxidant, an ultraviolet absorber, a sensitizing dye, a surfactant, a
color tone adjuster, a viscosity improver, an antibacterial agent, a pH adjuster,
a rust inhibitor, an emulsification stabilizer, a preservative, a defoamer, a viscosity
adjuster, a dispersion stabilizer, a chelating agent, a solid wetting agent, an organic
or inorganic salt, and the like.
[0105] Examples of the ultraviolet absorber include a benzophenone-based ultraviolet absorber,
a benzotriazole-based ultraviolet absorber, a salicylate-based ultraviolet absorber,
a cyanoacrylate-based ultraviolet absorber, a nickel complex-based ultraviolet absorber,
and the like.
[0106] As the antioxidant, it is possible to use a variety of organic and metal complex-based
discoloration preventers. Examples of the organic discoloration preventer include
hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes,
chromanes, alkoxyanilines, hetero rings, and the like. Examples of the metal complex-based
discoloration preventer include nickel complexes, zinc complexes, and the like.
[0107] Examples of the antibacterial agent include sodium dehydroacetate, sodium benzoate,
sodium pyridinethione-1-oxide, p-hydroxy ethyl benzoate ester, 1,2-benzisothiazoline-3-on,
sodium sorbate, pentachlorophenol sodium, and the like. The ink composition preferably
includes the antibacterial agent in a range of 0.02 mass% to 1.00 mass%.
[0108] There is no particular limitation regarding the pH adjuster as long as the pH adjuster
has no adverse influence on a curable composition to be adjusted, and is capable of
adjusting the pH to a desired value. Examples thereof include alcoholamines (for example,
diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propandiol, and the like), alkali
metal hydroxides (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide,
and the like), ammonium hydroxides (for example, ammonium hydroxide, quaternary ammonium
hydroxide, and the like), phosphonium hydroxide, alkali metal carbonate, and the like.
[0109] Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium
thioglycolate, diisopropyl ammonium nitrite, pentaerythritol tetranitrate, dicyclohexyl
ammonium nitrite, and the like.
[0110] Examples of the antioxidant include phenol-based antioxidants (including hindered
phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, phosphorous-based
antioxidants, and the like.
[0111] Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium
nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate,
sodium uramildiacetate, and the like.
[Properties of the curable resin composition]
[0112] The surface tension (25°C) of the curable resin composition of the present invention,
particularly, the ink composition is preferably in a range of 20 mN/m to 60 mN/m,
more preferably in a range of 20 mN/m to 45 mN/m, and still more preferably in a range
of 25 mN/m to 40 mN/m.
[0113] The surface tension is measured using an automatic surface tensiometer CBVP-Z (manufactured
by Kyowa Interface Science Co., Ltd.) under a condition in which the ink composition
is at 25°C.
[0114] The viscosity at 25°C is preferably in a range of 1.2 mPa·s to 15.0 mPa·s, more preferably
in a range of 2 mPavs to less than 13 mPa·s, and still more preferably in a range
of 2.5 mPa·s to less than 10 mPa·s.
[0115] The viscosity is measured using a VISCOMETER TV-22 (manufactured by Toki Sangyo Co.,
Ltd.) under a condition of 25°C.
[0116] From the viewpoint of the stability of the curable resin composition, particularly,
the ink composition, the pH is preferably in a range of 6 to 11. In a case in which
an ink set described below is produced, the ink composition preferably aggregates
at a high rate when coming into contact with the treatment fluid, and therefore the
pH is more preferably in a range of 7 to 10, and still more preferably in a range
of 7 to 9.
«Ink set»
[0117] An ink set of the present invention is made up of a part of the ink composition (hereinafter,
referred to as the ink composition A) which is the above-described curable resin composition
of the present invention and a part of an ink composition B which is the treatment
fluid containing an aggregating agent that is capable of forming an aggregate when
coming into contact with the ink composition A.
[0118] When an image is formed using the ink composition A and the treatment fluid containing
an aggregating agent, it is possible to form an image which has favorable image qualities,
high curing sensitivity, and excellent blocking resistance.
[0119] Hereinafter, the treatment fluid for the ink set will be described.
<Treatment fluid (acidic ink composition B)>
[0120] The acidic ink composition B (hereinafter, simply referred to as the treatment fluid)
which is the treatment fluid for the ink set preferably includes an acidic compound
that aggregates components in the ink composition, and may include other components
as necessary.
[Acidic compound]
[0121] In the present invention, the acid compound preferably has a molecular weight in
a range of 50 to 200, and pKa (25°C) in a range of 1 to 5 in water.
[0122] The acidic compound used in the treatment fluid is capable of aggregating (immobilizing)
the ink composition when coming into contact with the ink composition on a recording
medium, and functions as an immobilizing agent. For example, in a state in which an
aggregating agent is provided on a recording medium (preferably coated paper) by supplying
the treatment fluid to the recording medium, when the ink composition further lands
and comes into contact with the aggregating agent, the components in the ink composition
aggregate, and thus the ink composition can be immobilized onto the recording medium.
[0123] Preferable examples of the acidic compound include sulfuric acid, hydrochloric acid,
nitric acid, phosphoric acid, polyacrylic acid, acetic acid, glycolic acid, malonic
acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric
acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid,
metaphosphoric acid, pyrrolidone carboxylic acid, pyronecarboxylic acid, pyrrolecarboxylic
acid, furancarboxylic acid, pyridinecarboxylic acid, coumaric acid, thiophenecarboxylic
acid, nicotinic acid, oxalic acid, acetic acid, benzoic acid, derivatives thereof,
salts thereof, and the like. From the viewpoint of satisfying both the suppression
of volatilization and the degree of solubility in a solvent, the molecular weight
of the acidic compound is preferably in a range of 50 to 1000, more preferably in
a range of 50 to 500, and particularly preferably in a range of 50 to 200, and in
the ink set of the present invention, an acidic compound having a molecular weight
in a range of 50 to 200 is used. From the viewpoint of satisfying both the prevention
of ink bleeding and photocuring properties, an acidic compound having pKa (in H
2O) in a range of -10 to 7 is preferred, an acidic compound having pKa in a range of
1 to 7 is more preferred, and an acidic compound having pKa in a range of 1 to 5 is
particularly preferred, and in the ink set of the present invention, an acidic compound
having pKa in a range of 1 to 5 is used.
[0124] Among them, a highly water-soluble acidic compound is preferred. In addition, from
the viewpoint of immobilizing all the ink through a reaction with the ink composition,
a trivalent or lower acidic compound is preferred, and a divalent or trivalent acidic
compound is particularly preferred.
[0125] The acidic compound may be singly used, or two or more acidic compounds may be jointly
used.
[0126] In a case in which the treatment fluid includes the acidic compound, the pH (25°C)
of the treatment fluid is preferably in a range of 0.1 to 6.8, more preferably in
a range of 0.5 to 6.0, and still more preferably in a range of 0.8 to 5.0.
[0127] The content of the acidic compound is preferably 40 mass% or less, more preferably
in a range of 15 mass% to 40 mass%, still more preferably in a range of 15 mass% to
35 mass%, and particularly preferably in a range of 20 mass% to 30 mass% with respect
to the total mass of the treatment fluid. When the content of the acidic compound
is set in a range of 15 mass% to 40 mass%, it is possible to more efficiently immobilize
the components in the ink composition.
[0128] The amount of the acid compound supplied to a recording medium is not particularly
limited as long as the ink composition is aggregated; however, from the viewpoint
of ease of immobilizing the ink composition, the amount is preferably in a range of
0.5 g/m
2 to 4.0 g/m
2, and more preferably in a range of 0.9 g/m
2 to 3.75 g/m
2.
[Cationic polymer]
[0129] A cationic polymer is preferably at least one cationic polymer selected from poly(vinylpyridine)
salts, polyalkylaminoethylacrylate, polyalkylaminoethylmethacrylate, poly(vinylimidazole),
polyethylenimine, polybiguanide, and polyguanide.
[0130] Among the cationic polymers, polyguanide (preferably poly(hexamethylene guanidine)acetate,
polymonoguanide, polymeric biguanide), polyethylene imine, or poly(vinyl pyrridine),
which are advantageous from the viewpoint of the aggregation rate, is preferred.
[0131] The cationic polymer may be singly used, or two or more cationic polymers may be
jointly used.
[0132] The mass average molecular weight of the cationic polymer is preferably small from
the viewpoint of the viscosity of the treatment fluid. In a case in which the treatment
fluid is supplied to a recording medium by the ink jet method, the mass average molecular
weight is preferably in a range of 500 to 500,000, more preferably in a range of 700
to 200,000, and still more preferably in a range of 1,000 to 100,000. The mass average
molecular weight is advantageously 500 or more from the viewpoint of the aggregation
rate, and is advantageously 500,000 or less from the viewpoint of the discharge reliability.
In a case in which the treatment fluid is supplied to a recording medium using a method
other than the ink jet, what has been described above shall not apply.
[0133] The treatment fluid includes the cationic polymer, and the pH (25°C) of the treatment
fluid is preferably in a range of 1.0 to 10.0, more preferably in a range of 2.0 to
9.0, and still more preferably in a range of 3.0 to 7.0.
[0134] The content of the cationic polymer is preferably in a range of 1 mass% to 35 mass%,
and more preferably in a range of 5 mass% to 25 mass% with respect to the total mass
of the treatment fluid.
[0135] The amount of the cationic polymer supplied to coated paper is not particularly limited
as long as the ink composition is stabilized; however, from the viewpoint of ease
of immobilizing the ink composition, the amount is preferably in a range of 0.5 g/m
2 to 4.0 g/m
2, and more preferably in a range of 0.9 g/m
2 to 3.75 g/m
2.
«Photocuring method»
[0136] A photocuring method of the present invention is preferably a method in which the
resin composition is photocured by combining the ink composition (A) and the treatment
fluid [ink composition (B)], and is particularly preferably a method in which the
resin composition is cured under acidic conditions.
[0137] The acidic conditions refer to a fact that, when the ink composition is cured, the
environment of the ink composition or an environment in which the ink composition
is cured is an acidic condition, and as in the ink set described above, the ink composition
may be combined with another ink composition B.
[0138] In addition, the ink-receiving surface of a recording medium may be turned into an
acidic state using the ink composition B, or a recording medium having an ink-receiving
surface that has been in an acidic state in advance may be used.
[0139] During the photocuring, an active energy ray radiation step described below is preferably
applied.
«Image-forming method»
[0140] In an image-forming method of the present invention, the ink composition (ink composition
A) or the above-described photocuring method is used in an image-forming phase, and
the ink composition combined with a coloring agent may be used as a color image-forming
ink composition.
[0141] The image-forming method of the present invention preferably includes at least an
acid treatment step of supplying the ink composition B of the treatment fluid, which
is a part of the ink set, onto a recording medium (treatment fluid supply step), an
ink supply step of supplying the ink composition A onto the acid-treated recording
medium, and a photocuring step (active energy ray radiation step) of curing the ink
in a formed image through light radiation. In addition, the image-forming method may
further include other steps as necessary.
[Recording medium]
[0142] There is no particular limitation regarding the recording medium used in the image-forming
method of the present invention, and it is possible to use ordinary printing paper
which is used for ordinary offset printing and the like and includes cellulose as
a main body, such as so-called high-quality paper, coated paper, and art paper. On
ordinary printing paper including cellulose as a main body, when an image is recorded
using an ordinary ink jet method in which an aqueous ink is used, the absorption and
drying of ink is relatively slow, the transfer of a color material is likely to occur
after the striking of ink, and the image qualities are likely to degrade. However,
when an image is recorded using the ink jet recording method of the present invention,
the transfer of a color material is suppressed, and a high-quality image having excellent
color density and color tone can be recorded.
[0143] Commercially available ordinary paper can be used as the recording medium, and examples
thereof include "OK Prince High Quality" manufactured by Oji Paper Co., Ltd., "SHIRAOI"
manufactured by Nippon Paper Industries Co., Ltd., high-quality paper (A) such as
"NEW NPI High Quality" manufactured by Nippon Paper Industries Co., Ltd., high-quality
coated paper such as "SILVER DIAMOND" manufactured by Nippon Paper Industries Co.,
Ltd., fine coated paper such as "OK EVERLIGHT COAT" manufactured by Oji Paper Co.,
Ltd. and "AURORA S" manufactured by Nippon Paper Industries Co., Ltd., light-weight
coated paper (A3) such as "OK COAT L" manufactured by Oji Paper Co., Ltd. and "AURORA
L" manufactured by Nippon Paper Industries Co., Ltd., coated paper (A2, B2) such as
"OK TOP COAT+" manufactured by Oji Paper Co., Ltd. and "AURORA COAT" manufactured
by Nippon Paper Industries Co., Ltd., art paper (A1) such as "OK KANETO+" manufactured
by Oji Paper Co., Ltd. and "TOKUBISHI ART" manufactured by Mitsubishi Paper Mills
Limited, and the like. In addition, it is also possible to use a variety of photographic
paper for ink jet recording.
[0144] Among them, from the viewpoint of having a strong effect that suppresses the transfer
of a color material and the obtainment of a high-quality image having more favorable
color density and color tone than before, the water absorption coefficient Ka of the
recording medium is preferably in a range of 0.05 mL/m
2·ms
1/2 to 0.5 mL/m
2·ms
1/2, more preferably in a range of 0.1 mL/m
2·ms
1/2 to 0.4 mL/m
2·ms
1/2, and still more preferably in a range of 0.2 mL/m
2·ms
1/2 to 0.3 mL/m
2·ms
1/2.
[0145] The water absorption coefficient Ka is identical to that described in JAPAN TAPPI's
paper and pulp testing method No. 51:2000 (published by JAPAN TAPPI), and specifically,
the absorption coefficient Ka is computed from the difference in the amount of water
transferred between a contact duration 100 ms and a contact duration 900 ms using
an automatic scanning absorptometer KM500Win (manufactured by Kumagai Riki Kogyo Co.,
Ltd.).
[0146] Among the recording media, so-called coated paper, which is used for ordinary offset
printing, is preferred. The coated paper is paper obtained by applying a coating material
to the surface of high-quality paper, alkaline paper, or the like, which includes
cellulose as a main body, and is, generally, not subjected to a surface treatment,
thereby providing a coated layer. The coated paper is likely to cause a problem in
terms of quality such as the luster or wear resistance of an image in the formation
of the image by an ordinary aqueous ink jet; however, in a case in which the above-described
ink composition or ink set is used, luster variation is suppressed, and an image having
favorable shine properties and scratch resistance can be obtained. Particularly, coated
paper including base paper and a coated layer including kaolin and/or heavy calcium
bicarbonate is preferably used. More specifically, art paper, coated paper, light-weight
coated paper, or fine coated paper is more preferred.
[Acid treatment step (treatment fluid supply step)]
[0147] In the treatment fluid supply step, the treatment fluid containing an aggregating
agent included in the ink set is supplied onto the recording medium. For the supply
of the treatment fluid to the recording medium, a well-known liquid supply method
can be used with no particular limitation, and it is possible to select an arbitrary
method such as spray coating, coating by a coating roller or the like, supply by the
ink jet method, or immersion.
[0148] Specific examples thereof include size press methods represented by a horizontal
size press method, a roll coater method, a calendar size press method, and the like;
size press methods represented by an air knife coater method and the like; a knife
coater method represented by an air knife coater method and the like; transfer roll
coater methods such as a gate roll coater method and the like, roll coater methods
represented by a direct roll coater method, a reverse roll coater method, a squeeze
roll coater method, or the like; a bill blade coater method, and a short dwell coater
method; blade coater methods represented by a two stream coater method and the like;
bar coater methods represented by a rod bar coater method and the like; bar coater
methods represented by a rod bar coater method and the like; cast coater methods;
gravure coater methods; curtain coater methods; die coater methods; brush coater methods;
transfer methods, and the like.
[0149] In addition, it is also possible to use a method in which the treatment fluid is
applied by controlling the coating amount using a coating apparatus equipped with
a liquid amount restriction member such as the coating apparatus described in
JP1998-230201A (
JP-H10-230201A).
[0150] Regarding the region in which the treatment fluid is supplied, the supply may be
full-surface supply in which the treatment fluid is supplied to the entire recording
medium or partial supply in which the treatment fluid is partially supplied to regions
in which the ink is supplied in the ink supply step. In the present invention, from
the viewpoint of uniformly adjusting the amount of a treatment fluid supplied, homogeneously
recording fine lines, fine image portions, or the like, and suppressing the density
variation such as image variation, the full-surface supply in which the treatment
fluid is supplied to the entire coated paper through coating in which a coating roller
or the like is used is preferred.
[0151] Examples of a method for applying the treatment fluid by controlling the amount of
the treatment fluid supplied within the above-described range include a method in
which an anilox roller is used. The anilox roller refers to a roller provided with
pyramid shapes, diagonal lines, tortoiseshell shapes, or other shapes by processing
the surface of a roller on which ceramic has been sprayed using a laser. The treatment
fluid permeates into recess portions provided on the roller surface, and is transferred
to a paper surface when coming into contact with the paper surface, thereby applying
a controlled coating amount in the recesses of the anilox roller.
- Ink supply step -
[0152] In the ink supply step, the ink composition included in the ink set is supplied onto
the recording medium. There is no particular limitation regarding the method for supplying
the ink composition as long as the ink composition can be supplied in a desired image
pattern, and a well-known ink supply method can be used. For example, the ink composition
can be supplied onto the recording medium using means of the ink jet method, a mimeographing
method, a stamping method, or the like. Among them, from the viewpoint of compacting
a recording apparatus and high-speed recording properties, a step of supplying the
ink composition using the ink jet method is preferred.
[Ink jet method]
[0153] In the formation of an image using the ink jet method, the ink composition is discharged
onto the recording medium by supplying energy, and a colored image is formed. Meanwhile,
as a preferable ink jet recording method for the present invention, the method described
in paragraphs 0093 to 0105 in
JP2003-306623Acan be applied.
[0154] The ink jet method is not particularly limited, and may be a well-known method, for
example, any of a charge control method in which ink is discharged using an electrostatic
attracting force, a drop-on-demand method (a pressure pulse method) in which a vibration
pressure of a piezo element is used, an acoustic ink jet method in which ink is discharged
using radiation pressure by converting an electric signal to an acoustic beam, and
radiating the acoustic beam on the ink, and the like.
[0155] In addition, an ink jet head used in the ink jet method may be any of an on-demand
method and a continuous method. Furthermore, an ink nozzle and the like used when
recording is carried out using the ink jet method are not particularly limited, and
can be appropriately selected depending on the purpose.
[0156] The scope of the ink jet method includes a method in which a number of small volumes
of ink having a low concentration called photo ink are sprayed, a method in which
image qualities are improved using a plurality of inks having substantially the same
color tone and different concentrations, and a method in which colorless and transparent
ink is used.
[0157] As the ink jet method, there are a shuttle method in which recording is carried out
using a short serial head while the serial head is scanned in the width direction
of a recording medium and a line method in which a line head in which recording elements
are arrayed fully corresponding to one side of a recording medium is used. In the
line method, an image can be recorded on the entire surface of a recording medium
by scanning the recording medium in a direction orthogonal to the array direction
of the recording elements, and a transportation system such as a carriage that scans
the short head becomes unnecessary. In addition, the movement of the carriage and
the complicated scanning control with a recording medium become unnecessary, and only
the recording medium is moved, and therefore the recording speed can be increased
compared with the shuttle method.
[0158] In the present invention, there is no particular limitation regarding the order of
the acid treatment step and the ink supply step; however, from the viewpoint of image
quality, it is preferable to carry out the ink supply step after the acid treatment
step. That is, the ink supply step is preferably a step of supplying the ink composition
onto the recording medium onto which the acid treatment agent has been supplied.
[Active energy ray radiation step]
[0159] In the image-forming method of the present invention, a step of radiating an active
energy ray on the ink composition supplied onto the recording medium is preferably
included. When an active energy ray is radiated, the polymerizable compound included
in the ink composition is polymerized, and a cured film including the colorant is
formed. As a result, the scratch resistance and blocking resistance of an image are
more effectively improved.
[0160] The ink composition supplied onto the recording medium is cured when being irradiated
with an active energy ray. This is because the photopolymerization initiator included
in the ink composition is decomposed by the radiation of the active energy ray, a
radical is generated, and the polymerization reaction of the polymerizable compound
is initiated and accelerated by the generated radical, whereby the ink composition
is cured.
[0161] In a case in which an acid is included in the treatment fluid, the ink composition
is further aggregated (immobilized) by the acid supplied from the compound when the
active energy ray is radiated, and the qualities of an image section (scratch resistance,
blocking resistance, and the like) improve.
[0162] In the present invention, as the active energy ray, an α ray, a y ray, an electron
beam, an X ray, an ultraviolet ray, a visible ray, an infrared ray, and the like can
be used. As described above, the photopolymerization initiator used in the present
invention strongly absorbs, particularly, light in the ultraviolet range, and therefore
the wavelength of the active energy ray is preferably in a range of 200 nm to 600
nm, more preferably in a range of 300 nm to 450 nm, and still more preferably in a
range of 350 nm to 420 nm.
[0163] The output of the active energy ray is preferably 5000 mJ/cm
2 or less, more preferably in a range of 10 mJ/cm
2 to 4000 mJ/cm
2, and still more preferably in a range of 20 mJ/cm
2 to 3000 mJ/cm
2.
[0164] As an active energy ray source, a mercury lamp, a gas or solid laser, and the like
are mainly used, and, as a light source used for the curing of ink for ultraviolet
photo-curing ink jet recording, a mercury lamp or a metal halide lamp is widely known.
However, currently, there is a strong demand for the removal of mercury from the viewpoint
of environmental protection, and the substitution into a GaN-based semiconductor ultraviolet
light-emitting device is extremely useful in terms of industrial and environmental
senses. In addition, an LED and an LD are small and inexpensive, and have performance
of a long service life and high efficiency, and therefore they are expected as light
sources for a photo-curing ink jet.
[0165] In the present invention, a light emitting diode (LED) and a laser diode (LD) can
be used as the active energy ray source. Particularly, an ultraviolet LED (UV-LED)
and an ultraviolet LD (UV-LD) can be used as an ultraviolet ray source. For example,
Nichia Corporation sells a purple LED in which the main emission spectrum has a wavelength
between 365 nm and 420 nm.
[0166] A particularly preferable active energy ray source in the present invention is a
UV-LED, and a UV-LED having a peak wavelength in a range of 350 nm to 420 nm is preferred.
[Ink-drying step]
[0167] The image-forming method of the present invention may include, if necessary, an ink-drying
step in which the solvent (for example, water, the above-described aqueous medium,
or the like) in the ink composition supplied onto the recording medium is dried and
removed. The ink-drying step is not particularly limited as long as at least a part
of the ink solvent can be removed, and it is possible to apply a generally-used method.
[Curable resin composition for usages other than the ink composition]
[0168] In addition to the ink composition, the curable resin composition of the present
invention is useful as a curable resin composition that cures a variety of resins.
[0169] Particularly, the curable resin composition of the present invention contains water,
and thus is used as a water-soluble or emulsion-based curable resin composition.
[0170] Examples thereof include paint, adhesives, gluing agents, functional coating agents,
a variety of coats, a variety of films, optical materials, printing plate materials,
semiconductor materials, recording materials, tissue culturing plates, paper additives,
medical materials, plastic, water retention agents, water absorption agents, hydrophilic
members, and the like.
[0171] More specific examples thereof include antireflection layers in a variety of films,
base coat adhesive layers in a variety of films, coating layers in a variety of films,
resists, press plates, color filters, endoscope coating agents, ion-exchange membranes,
reverse osmosis membranes, conductive coated films, medical adhesives, proton-conducting
membranes, micropore films, and the like.
Examples
[0172] Hereinafter, the present invention will be described in more detail on the basis
of examples, but the present invention is not limited to these examples.
Example 1
[Preparation of a polymerizable compound]
[0173]
[Synthesis of Polymerizing Compound M-1]
[0174] 40.0 g (182 mmol) of 4,7,10-trioxa-1,13-tridecanediamine, 37.8 g (450 mmol) of sodium
hydrogen carbonate, 100 g of water, and 200 g of tetrahydrofuran were added to a 1L
three neck flask including a stirrer. 35.2 g (389 mmol) of acrylic acid chloride was
added dropwise to the mixture for 20 minutes in an ice bath, and the solution was
stirred at room temperature for five hours after the dropwise addition. Tetrahydrofuran
was distilled away from the obtained reaction mixture at reduced pressure. Next, a
product was extracted from a water layer four times using 200 ml of ethyl acetate,
the obtained organic layer was dried using magnesium sulfate, and then was filtered,
and a solvent was distilled away at reduced pressure, thereby obtaining 35.0 g (107
mmol, yield 59%) of target solid Polymerizing Compound M-2.
[Preparation of photopolymerization initiator]
[Synthesis of Photopolymerization Initiator I-1]
[Synthesis of Photopolymerization Initiator I-2]
[Synthesis of Photopolymerization Initiator I-5]
[0177] Photopolymerization Initiator I-5 was synthesized with reference to
JP2009-84220A according to the following scheme.
[Synthesis of Photopolymerization Initiator I-3]
[0178] Photopolymerization Initiator I-3 was synthesized with reference to
Angwe. Chem. Int. Ed., 46, 8869 (2007) and the synthesis method of Photopolymerization Initiator I-1 according to the following
scheme.
[Synthesis of Photopolymerization Initiator I-8]
[0179] Photopolymerization Initiator I-8 was synthesized with reference to the specification
of
US4,190,602A and the synthesis method of Photopolymerization Initiator I-1 according to the following
scheme.
[Synthesis of Photopolymerization Initiator I-4]
[0180] Photopolymerization Initiator I-4 was synthesized with reference to
J. Am. Chem. Soc., 131, 4227 (2009) and the synthesis method of Photopolymerization Initiator I-1 according to the following
scheme.
[Preparation of comparative example Compounds]
[Synthesis of Polymer Dispersing agent P-1]
[0182] 88 g of methyl ethyl ketone was added to a 1000 ml three neck flask including a stirrer
and a cooling pipe, was heated at 72°C in a nitrogen atmosphere, and a solution obtained
by dissolving 0.85 g of dimethyl 2,2'-azobisisobutyrate, 60 g of benzyl methacrylate,
10 g of methacrylic acid, and 30 g of methyl methacrylate in 50 g of methyl ethyl
ketone was added dropwise to the methyl ethyl ketone for three hours. After the dropwise
addition, the components were further reacted for one hour, then, a solution obtained
by dissolving 0.42 g of dimethyl 2,2'-azobisisobutyrate in 2 g of methyl ethyl ketone
was added, and was heated at 78°C for four hours. The obtained reaction solution was
re-precipitated twice in an extremely excessive amount of hexane, and the reduced
resin was dried, thereby obtaining 96 g of Polymer Dispersing agent P-1.
[0183] The composition of the obtained resin was confirmed through
1H-NMR, and the mass-average molecular weight (Mw) obtained through gel permeation
chromatography (GPC) was 44,600. Furthermore, as a result of obtaining the acid value
using the method described in JIS standards (JISK0070:1992), the acid value was 65.2
mgKOH/g.
[Preparation of a resin-coated pigment-dispersion]
- Resin-coated magenta pigment dispersion -
[0184] 10 parts by mass of Chromophthal Jet Magenta DMQ (Pigment Red 122, manufactured by
BASF Japan Ltd.), 5 parts by mass of Polymer Dispersing agent P-1, 42 parts by mass
of methyl ethyl ketone, 5.5 parts by mass of an aqueous solution of 1 mol/L NaOH,
and 87.2 parts by mass of ion exchange water were mixed together, and were dispersed
for two hours to six hours using a beads mill in which 0.1 mmφ zirconia beads were
used.
[0185] Methyl ethyl ketone was removed from the obtained dispersed substance at reduced
pressure at 55°C, and furthermore, some of the water was removed, thereby obtaining
a resin-coated magenta pigment dispersion (coloring particles) having a pigment concentration
of 10.2 mass%.
[Preparation of Ink Sets 1 to 7 and Comparative Ink Sets c1 to c6]
[0186] Magenta Inks 1 to 7, Comparative Magenta Inks c1 to c6, and Treatment Fluids 1 and
2 were respectively prepared as described below, and Ink Sets 1 to 5 and 7, and Comparative
Inks Sets c1 to c6, which were combinations of the respective ink compositions of
Magenta Inks 1 to 5 and 7 and Comparative Magenta Inks c1 to c6, and Treatment Fluid
1, were obtained. In addition, Ink Set 6, which was a combination of Magenta Ink 6
and Treatment Fluid 2, was obtained.
(Preparation of Magenta Inks 1 to 7)
[0187] As described below, a resin-coated magenta pigment dispersion, ion exchange water,
a photopolymerization initiator, a polymerizable compound, and a surfactant were mixed
using the resin-coated magenta pigment dispersion, and then the mixture was filtered
using a 5 µm membrane filter, thereby preparing Magenta Inks 1 to 4 and Comparative
Magenta Inks c1 to c6.
- Preparation of Magenta Ink 1 -
[0188]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound I-1 (water-soluble photopolymer initiator) 1 mass%
- N-methyl diethanolamine (produced by Tokyo Chemical Industry Co., Ltd.) 1 mass%
- Polymerizing Compound M-1 15 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Magenta Ink 2 -
[0189]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound I-2 (water-soluble photopolymer initiator) 2 mass%
- Polymerizing Compound M-1 15 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Magenta Ink 3 -
[0190]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound I-5 (water-soluble photopolymer initiator) 1 mass%
- N-methyl diethanolamine (produced by Tokyo Chemical Industry Co., Ltd.) 1 mass%
- Polymerizing Compound M-1 15 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Magenta Ink 4 -
[0191]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound I-3 (water-soluble photopolymer initiator) 1 mass%
- N-methyl diethanolamine (produced by Tokyo Chemical Industry Co., Ltd.) 1 mass%
- Polymerizing Compound M-1 15 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Magenta Ink 5 -
[0192]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound I-8 (water-soluble photopolymer initiator) 2 mass%
- Polymerizing Compound M-1 15 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Magenta Ink 6 -
[0193]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound I-4 (water-soluble photopolymer initiator) 2 mass%
- Polymerizing Compound M-1 15 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Magenta Ink 7 -
[0194]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound I-1 (water-soluble photopolymer initiator) 1 mass%
- N-methyl diethanolamine (produced by Tokyo Chemical Industry Co., Ltd.) 1 mass%
- Polymerizing Compound M-1 15 mass%
- NDSB-256 (produced by Wako Pure Chemical Industries, Ltd.; betaine-type surfactant)
1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
[0195] As a result of measuring the pHs (25°C) of Magenta Inks 1 to 4 using a pH meter WM-50EG
(manufactured by DKK-Toa Corporation), the pH values were all 8.5.
- Preparation of Comparative Magenta Ink c1 -
[0196]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound R-1 (water-soluble photopolymer initiator) 2 mass%
- Polymerizing Compound M-1 15 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Comparative Magenta Ink c2 -
[0197]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound R-2 (water-soluble photopolymer initiator) 1 mass%
- N-methyl diethanolamine (produced by Tokyo Chemical Industry Co., Ltd.) 1 mass%
- Polymerizing Compound M-1 15 mass%
- Olefin E1010 1 mass%
(produced by Nissin Chemical Co., Ltd.; surfactant)
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Comparative Magenta Ink c3 -
[0198]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound R-3 (water-soluble photopolymer initiator) 4 mass%
- Polymerizing Compound M-1 10 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
[0199] - Preparation of Comparative Magenta Ink c4 -
- Resin-coated magenta pigment dispersion 6 mass%
- Compound R-4 (water-soluble photopolymer initiator) 4 mass%
- Polymerizing Compound M-1 10 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Comparative Magenta Ink c5 -
[0200]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound R-1 (water-soluble photopolymer initiator) 3 mass%
- Polymerizing Compound M-1 10 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- NDSB-256 (produced by Wako Pure Chemical Industries, Ltd.; betaine-type surfactant)
3 mass%
- Ion exchange water added so that the total amount reached 100 mass%
- Preparation of Comparative Magenta Ink c6 -
[0201]
- Resin-coated magenta pigment dispersion 6 mass%
- Compound R-2 (water-soluble photopolymer initiator) 3 mass%
- N-methyl diethanolamine (produced by Tokyo Chemical Industry Co., Ltd.) 3 mass%
- Polymerizing Compound M-1 10 mass%
- Olefin E1010 (produced by Nissin Chemical Co., Ltd.; surfactant) 1 mass%
- NDSB-256 (produced by Wako Pure Chemical Industries, Ltd.; betaine-type surfactant)
3 mass%
- Ion exchange water added so that the total amount reached 100 mass%
[Preparation of treatment fluid]
[0202] Materials described below were mixed, thereby producing Treatment Fluid 1. As a result
of measuring the pH (25°C) of Treatment Fluid 1 using a pH meter WM-50EG (manufactured
by DKK-Toa Corporation), the pH was 1.0.
- Composition of Treatment Fluid 1 -
[0203]
- Malonic acid 25 mass%
- Tripropylene glycol monomethyl ether (water-soluble organic solvent) 5 mass%
- Ion exchange water 70 mass%
- Composition of Treatment Fluid 2 -
[0204]
- Malonic acid 30 mass%
- 2-mercaptobenzothiazole 5 mass%
- Acetonitrile 30 mass%
- Tripropylene glycol monomethyl ether (water-soluble organic solvent) 5 mass%
- Ion exchange water 30 mass%
[Ink jet recording]
[0205] As a recording medium (coated paper), Tokubishi Art double-sided N paper (manufactured
by Mitsubishi paper Mills Limited) (basis weight 104.7 g/m
2) was prepared, an image was formed as described below, and the formed image was evaluated
as described below.
[0206] Line images and solid images were formed through four-color single pass recording
using Ink Sets 1 to 7 and Comparative Ink Sets c1 to c6 prepared above.
[0207] At this time, regarding the line images, line images were formed in forms of a line
as wide as one 1200 dpi dot, a line as wide as two dots, and a line as wide as four
dots by discharging the ink compositions in the main scanning direction through a
single pass.
[0208] In addition, the solid images were formed by discharging the ink compositions to
all the entire surfaces of samples obtained by cutting the recording medium into the
A5 size. A variety of conditions for forming the images are as described below.
(1) Treatment fluid supply step
[0209] The treatment fluids were applied to all the entire surfaces of the recording media
using a roll coater in which the application amount was controlled using an anilox
roller (the number of lines per inch was in a range of 100 to 300) so that the supply
amount reached 1.4 g/m
2.
(2) Treatment step
[0210] Next, on the recording media to which the treatment fluids had been applied, a drying
treatment and a permeation treatment were carried out under the following conditions.
- wind speed: 10 m/s
- Temperature: the recording medium was heated using a contact-type planar heater from
the side (rear surface side) opposite to the recording surface side of the recording
medium so that the surface temperature of the recording medium on the recording surface
side reached 60°C.
(3) Ink supply step
[0211] After that, the ink compositions were discharged using the ink jet method under the
following conditions to the coated surfaces of the recording media on which the treatment
fluids had been applied, thereby forming line images and solid images respectively.
- Head: as many as four colors of piezo full line heads as wide as 1,200 dpi/20 inch
were disposed
- Amount of liquid droplets discharged: 2.0 pL
- Driving frequency: 30 kHz
(4) Ink-drying step
[0212] Next, the recording media to which the ink compositions had been supplied were dried
under the following conditions.
- Drying method: blast drying
- Wind speed: 15 m/s
- Temperature: the recording medium was heated using a contact-type planar heater from
the side (rear surface side) opposite to the recording surface side of the recording
medium so that the surface temperature of the recording medium on the recording surface
side reached 60°C.
(5) Immobilizing step
[0213] Next, an ultraviolet ray was radiated on the recorded images as the active energy
ray using a metal halide lamp under an energy condition of 1000 mJ/cm
2, thereby obtaining image records.
[Evaluation]
[0214] The degrees of solubility of the polymerization initiators, the stability of the
inks, and the curing properties of the obtained image records were tested as described
below.
[Degree of solubility]
[0215] 3 mass% aqueous solutions were respectively prepared using Polymerization Initiators
1-1 to I-5, I-8, and R-1 to R-4, and the degrees of solubility of the polymerization
initiators were evaluated according to the following evaluation standards.
- Evaluation standards -
[0216]
- A: The polymerization initiator was fully dissolved at room temperature.
- B:The polymerization initiator was slightly precipitated at room temperature, and
was fully dissolved when being heated at 60°C.
- C:The polymerization initiator was not fully dissolved even when being heated at 60°C.
[Ink stability]
[0217] Magenta Inks 1 to 7 and Comparative Magenta Inks c1 to c6 were subjected to two-hour
temporal tests in a constant-temperature tank at 60°C, and were evaluated according
to the following evaluation standards.
- Evaluation standards -
[0218]
- A: The aggregation of the ink was not visible.
- B:The aggregation of the ink was slightly visible.
- C:The aggregation of the ink was visible, and was at a level causing a practical problem.
- Curing sensitivity -
[0219] Non-printed Tokubishi Art double-sided N paper (manufactured by Mitsubishi paper
Mills Limited) was coiled around a paperweight (mass 470 g, size: 15 mmx30 mm×120
mm) (the contact area between the non-printed Tokubishi Art and a recorded image was
150 mm
2), and the recorded image was rubbed three times (equivalent of a load of 260 kg/m
2). The rubbed print surface was visually observed, and was evaluated according to
the following evaluation standards.
- Evaluation standards -
[0220]
A ··· The image (color material) on the printed surface was not peeled off.
B ··· The image (color material) on the printed surface was slightly peeled off.
C ··· The image (color material) on the printed surface was peeled off, and was at
a level causing a practical problem.
[0221] The obtained results are described in Table 1 described below.
[Table 1]
Ink set No. |
Polymerization initiator |
Surfactant |
Treatment fluid |
Degree of solubility |
Ink stability |
Curing sensitivity |
Note |
1 |
I-1 |
Olefin E1010 |
1 |
A |
A |
A |
Present Invention |
2 |
I-2 |
Olefin E1010 |
1 |
A |
A |
A |
Present Invention |
3 |
I-5 |
Olefin E1010 |
1 |
A |
A |
A |
Present Invention |
4 |
I-3 |
Olefin E1010 |
1 |
A |
A |
A |
Present Invention |
5 |
I-8 |
Olefin E1010 |
1 |
A |
A |
A |
Present Invention |
6 |
I-4 |
Olefin E1010 |
2 |
A |
A |
A |
Present Invention |
7 |
I-1 |
NDSB-256 |
1 |
A |
A |
A |
Present Invention |
c1 |
R-1 |
Olefin E1010 |
1 |
C |
A |
B |
Comparative Example |
c2 |
R-2 |
Olefin E1010 |
1 |
A |
C |
A |
Comparative Example |
c3 |
R-3 |
Olefin E1010 |
1 |
C |
C |
C |
Comparative Example |
c4 |
R-4 |
Olefin E1010 |
1 |
A |
B |
A |
Comparative Example |
c5 |
R-1 |
NDSB-256 |
1 |
C |
A |
B |
Comparative Example |
c6 |
R-2 |
NDSB-256 |
1 |
A |
C |
A |
Comparative Example |
[0222] As is clear from the results of Table 1, the images formed using the photopolymerization
initiators having the betaine structure were favorable in terms of both the ink stability
and the curing sensitivity compared with the images formed using the photopolymerization
initiator of the related art which did not have the betaine structure.
[0223] In Ink Sets c5 and c6, a combination of the photopolymerization initiator of the
related art which did not have the betaine structure and the betaine-type surfactant
was used, but the effects of the present invention were not obtained.